Vehicle position detector, automatic steering controller, vehicle position detecting method, and automatic steering control method

ABSTRACT

A vehicle position detector includes: a satellite positioning receiver; an autonomous navigation processor outputting an own-vehicle position as an autonomous navigation position; a determining unit determining occurrence of a position jump on the basis of a positional difference between the autonomous navigation position and a satellite positioning position detected by the satellite positioning receiver using satellite positioning; and a selector selecting one of the autonomous navigation position and the satellite positioning position on the basis of positioning precision of satellite positioning output by the satellite positioning receiver, and a result of the determination, wherein the vehicle position detector outputs one of the autonomous navigation position and the satellite positioning position as the own-vehicle position on the basis of a result of the selection.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of U.S. patent applicationSer. No. 15/617,037 filed Jun. 8, 2017, which claims priority fromJapanese Patent Application No. 2016-153374 filed Aug. 4, 2016, thecontents of which are incorporated herein by reference in theirentireties.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a vehicle position detector that candetect an own-vehicle position with high precision, and an automaticsteering controller that controls automatic driving of a vehicle on thebasis of the own-vehicle position.

Description of the Background Art

Recent years have seen the development of self-driving vehicles thatcompute a target driving route using own-vehicle position informationand map information that are highly precise and obtained from satellitesand then can be automatically driven along the target driving route.

Although the automatic driving is predicated upon obtainment of highlyprecise own-vehicle position information, the position data obtainedfrom satellites is subject to the environment surrounding the vehicleand thus a position jump by which the data largely alters may occur.

In order to address such a position jump, for example, Japanese PatentApplication Laid-Open No. 2013-122406 discloses a technique fordetecting a position jump of an object by calculating an estimatedposition of the object and calculating a difference between theestimated position and a measured position obtained from a satellite.

When the position jump is detected, the own-vehicle position iscorrected. In Japanese Patent Application Laid-Open No. 2013-122406, theprocesses require time longer than the update cycle of satelliteinformation, thus causing a problem in that precise own-vehicle positioninformation cannot be obtained over a long period of time.

Furthermore, the correction of the own-vehicle position may consequentlyinfluence the automatic steering (steering operation) of theself-driving vehicles that perform automatic driving on the basis ofown-vehicle position information, and destabilize the vehicle behaviorsuch as occurrence of sudden route change.

SUMMARY OF THE INVENTION

Provided is a vehicle position detector that can immediately obtainprecise own-vehicle position information. The vehicle position detectorincludes a satellite positioning receiver, an autonomous navigationprocessor, a determining unit, and a selector. The autonomous navigationprocessor outputs an own-vehicle position detected by the autonomousnavigation as an autonomous navigation position. The determining unitdetermines occurrence of a position jump on the basis of a positionaldifference between the autonomous navigation position and a satellitepositioning position detected by the satellite positioning receiverusing the satellite positioning. The selector selects one of theautonomous navigation position and the satellite positioning position onthe basis of positioning precision of the satellite positioning that isoutput by the satellite positioning receiver, and a result of thedetermination on position jump by the determining unit. The vehicleposition detector outputs one of the autonomous navigation position andthe satellite positioning position as the own-vehicle position on thebasis of a result of the selection by the selector.

According to the present invention, it is possible to immediately obtainthe precise own-vehicle position information.

These and other objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an overall structure of aself-driving vehicle to which the present invention is to be applied;

FIG. 2 is a block diagram illustrating a configuration of an own-vehicleposition detector;

FIG. 3 is a flowchart for describing the overall operations of theown-vehicle position detector;

FIG. 4 is a flowchart for describing the overall operations of acorrection setting unit;

FIG. 5 is a block diagram illustrating a configuration of a positionjump determining unit;

FIG. 6 is a flowchart for describing an operation of a correctionselector;

FIG. 7 is a diagram indicating selection conditions for selectingwhether to correct a position;

FIG. 8 schematically illustrates a relationship between a threshold fordetermining occurrence of a position jump and a positional difference;

FIG. 9 schematically illustrates operations after determining that aposition jump has occurred;

FIG. 10 is a diagram indicating a steering wheel angle using automaticsteering when a position jump occurs;

FIG. 11 is a diagram indicating a lateral acceleration using automaticsteering when a position jump occurs;

FIG. 12 schematically illustrates a misalignment in detecting a positionjump by a conventional method when a position jump occurs; and

FIG. 13 schematically illustrates a misalignment according to thepresent invention when a position jump occurs.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment

FIG. 1 is a block diagram illustrating an overall structure of aself-driving vehicle 1 capable of automatic driving as an example of avehicle to which the present invention is applicable.

As illustrated in FIG. 1, the self-driving vehicle 1 includes a steeringwheel 3 that operates two of tires 2 as front wheels and that isequipped with an electric power steering (EPS) motor/controller 4 in anEPS system, and has a structure in which the EPS motor/controller 4allows automatic steering of the steering wheel 3 on the basis of acontrol signal obtained from an automatic steering controller 11.

The automatic steering controller 11 is also referred to as an advanceddriving assistance systems-electronic control unit (ADAS-ECU). Theautomatic steering controller 11 computes a target driving route on thebasis of the highly precise map information stored in a map informationstorage 10 and the own-vehicle position information that is highlyprecise and detected by an own-vehicle position detector 9, and providesautomatic steering and controls the velocity and the brake for thesteering wheel 3 according to the target driving route.

Each of the two tires 2 includes a velocity sensor 5 that measures thenumber of rotations of the tire 2 to calculate the velocity and providesthe velocity to the automatic steering controller 11. The method forobtaining the velocity is not limited to such.

Furthermore, a yaw rate sensor 6 measures a yaw rate (a rate of changeof angular velocity in a rotation direction) of the vehicle and providesit to the automatic steering controller 11.

The own-vehicle position detector 9 detects (computes) a position of theown vehicle on the basis of an satellite signal received from anartificial satellite 8 such as a global navigation satellite system(GNSS) or a quasi-zenith satellite through an antenna 7, and providesthe own-vehicle position information to the automatic steeringcontroller 11. Furthermore, the velocity sensors 5, the yaw rate sensor6, for example, an acceleration sensor, a gyro sensor, and an azimuthsensor that are not illustrated are connected to the own-vehicleposition detector 9 to allow autonomous navigation (inertial navigation)for autonomously detecting the position of the own vehicle on the basisof the information provided from each of the sensors.

Although the automatic steering controller 11 computes a target drivingroute on the basis of the highly precise own-vehicle positioninformation detected by the own-vehicle position detector 9 in the abovedescription, the own-vehicle position detector 9 may compute the targetdriving route on the basis of the highly precise map information and theown-vehicle position information and provide the target driving routeinformation to the automatic steering controller 11.

Next, the configuration of the own-vehicle position detector 9 will bedescribed with reference to the functional block diagram in FIG. 2. Asillustrated in FIG. 2, the own-vehicle position detector 9 includes asatellite positioning receiver 21, a direction processor 22, acorrection setting unit 23, an autonomous navigation processor 24, aposition jump determining unit 25, and a correction selector 26.

The satellite positioning receiver 21 reads a satellite signal(GNSS_Signal) received through the antenna 7, and performs predeterminedcomputation to output a precision indicator (GNSS_Quality) and asatellite positioning position (GNSS_Pos). Here, examples of thesatellite positioning receiver 21 include a real-time kinematic (RTK)receiver that capable of RTK measurement.

In the RTK measurement, a moving object can be measured within aprecision of a few centimeters. In other words, in the RTK measurement,a distance between a satellite and a receiver is obtained from thenumber of carriers and the phase difference to identify a positionwithin a precision of a few centimeters.

When the RTK receiver estimates an integer portion of a wave number in areal number, the precision is defined as “Float” ranging from severaltens of centimeters to 1 meter. When the RTK receiver fixes the integerportion of the wave number in an integer, the precision is defined as“Fix” ranging from 5 mm to 20 mm.

The satellite positioning receiver 21 outputs a satellite positioningposition in both “Float” and “Fix”. Furthermore, the satellitepositioning receiver 21 outputs, as a precision indicator(GNSS_Quality), 1 indicating higher precision (first precision) in“Fix”, and 0 indicating lower precision (second precision) in “Float”.

In the RTK measurement, the satellite positioning receiver 21 in areference station simultaneously performs positioning of the referencestation whose position is fixed and a mobile station whose position isunknown. The reference station wirelessly transmits the observed data tothe mobile station, and the satellite positioning receiver 21 obtainsthe position of the mobile station on the basis of the position of thereference station. Although the satellite positioning receiver 21 has astructure of receiving the positioning augmentation information based onthe result of positioning by a fixed station to be a reference station,through a wireless communication system such as information transmittedfrom a mobile phone or an artificial satellite, an illustration of sucha structure is omitted.

The direction processor 22 receives the satellite positioning position(GNSS_Pos), and computes a satellite positioning direction(GNSS_Direction), that is, a moving direction of the own vehicle. Thiscomputation is to obtain the moving direction (east, west, north andsouth) of the own vehicle by comparing the position of the own vehicleobtained with update timing of a previous satellite signal, with aposition (current position) of the own vehicle obtained with updatetiming of a current satellite signal. The correction setting unit 23receives the obtained satellite positioning direction (GNSS_Direction).

The correction setting unit 23 receives, besides the satellitepositioning direction (GNSS_Direction), the satellite positioningposition (GNSS_Pos) output from the satellite positioning receiver 21and a selection result (Select_SW) output from the correction selector26. When the position of the own vehicle is not corrected, thecorrection setting unit 23 outputs to the autonomous navigationprocessor 24 an autonomous maintaining signal (At_M) instructing that anautonomous navigation position (At_Pos) and an own-vehicle direction(Direction) should be maintained. Furthermore, the correction settingunit 23 sets a duration of detection of a position jump (T_Count), andoutputs it to the position jump determining unit 25. When the positionof the own vehicle is corrected, the correction setting unit 23 outputsto the autonomous navigation processor 24 a corrected position(C_GNSS_Pos) and a corrected direction (C_Direction).

The autonomous navigation processor 24 receives the yaw rate (Yawrate)measured by the yaw rate sensor 6 and the velocity (Vel) measured by thevelocity sensor 5, and computes the autonomous navigation position(At_Pos) and the own-vehicle direction (Direction) on the basis of theseinputs. Upon receipt of the corrected position (C_GNSS_Pos) and thecorrected direction (C_Direction) from the correction setting unit 23,the autonomous navigation processor 24 outputs the autonomous navigationposition (At_Pos) and the own-vehicle direction (Direction) that arecomputed, instead of the corrected position (C_GNSS_Pos) and thecorrected direction (C_Direction). Upon receipt of the autonomousmaintaining signal (At_M) from the correction setting unit 23, theautonomous navigation processor 24 outputs the autonomous navigationposition (At_Pos) and the own-vehicle direction (Direction) that arecomputed.

The position jump determining unit 25 receives, besides the duration ofdetection of the position jump (T_Count) output from the correctionsetting unit 23, the satellite positioning position (GNSS_Pos) outputfrom the satellite positioning receiver 21 and the autonomous navigationposition (At_Pos) output from the autonomous navigation processor 24.The position jump determining unit 25 determines occurrence of aposition jump on the basis of these inputs, and outputs to thecorrection selector 26 a result of the determination on position jump(PosJump_Judge).

The correction selector 26 receives, besides the result of thedetermination on position jump (PosJump_Judge), the precision indicator(GNSS_Quality) output from the satellite positioning receiver 21. Thecorrection selector 26 outputs a selection result (Select_SW) indicatingwhether the position is to be corrected on the basis of these inputs.

Next, the overall operations of the vehicle position detector 9 will bedescribed with reference to the flowchart in FIG. 3.

The satellite positioning receiver 21 reads a satellite signal withpredetermined update timing, and performs predetermined computation tooutput the precision indicator (GNSS_Quality) and the satellitepositioning position (GNSS_Pos) (Step S101).

The direction processor 22 computes a moving direction of the ownvehicle on the basis of the satellite positioning position (GNSS_Pos)received from the satellite positioning receiver 21 (Step S102).

When the position of the own vehicle is not corrected on the basis ofthe selection result (Select_SW), the correction setting unit 23 outputsto the autonomous navigation processor 24 the autonomous maintainingsignal (At_M), and sets the duration of detection of the position jump(T_Count) to output it to the position jump detecting unit 25. When theposition of the own vehicle is corrected on the basis of the selectionresult (Select_SW), the correction setting unit 23 outputs to theautonomous navigation processor 24 the corrected position (C_GNSS_Pos)and the corrected direction (C_Direction) (Step S103).

Upon receipt of the autonomous maintaining signal (At_M) from thecorrection setting unit 23, the autonomous navigation processor 24computes the autonomous navigation position (At_Pos) and the own-vehicledirection (Direction) on the basis of the yaw rate (Yawrate) measured bythe yaw rate sensor 6 and the velocity (Vel) measured by the velocitysensor 5 to output the results. Upon receipt of the corrected position(C_GNSS_Pos) and the corrected direction (C_Direction) from thecorrection setting unit 23 instead of the autonomous maintaining signal(At_M), the autonomous navigation processor 24 outputs the correctedposition (C_GNSS_Pos) and the corrected direction (C_Direction) insteadof the autonomous navigation position (At_Pos) and the own-vehicledirection (Direction) that have been computed (Step S104).

The position jump determining unit 25 determines occurrence of aposition jump on the basis of the duration of detection of the positionjump (T_Count) output from the correction setting unit 23, the satellitepositioning position (GNSS_Pos) output from the satellite positioningreceiver 21, and the autonomous navigation position (At_Pos) output fromthe autonomous navigation processor 24, and outputs, to the correctionselector 26, 1 indicating that the position of the own vehicle is to becorrected, and 0 indicating that the position of the own vehicle is notcorrected as a result of the determination on position jump(PosJump_Judge) (Step S105).

The correction selector 26 selects whether to correct the position onthe basis of the result of the determination on position jump(PosJump_Judge) and the precision indicator (GNSS_Quality) output fromthe satellite positioning receiver 21, and outputs the selection result(Select_SW) to the correction setting unit 23 (Step S106).

Next, the configuration and the operations of each of the functionalblocks of the own-vehicle position detector 9 will be described withreference to FIGS. 4 to 7. FIG. 4 is a flowchart for describingoperations of the collection setting unit 23. The collection settingunit 23 is set to cyclically repeat the operations. Once the correctionsetting unit 23 starts the operations, a time counter inside startscounting the time (Step S201). The operating cycle of the correctionsetting unit 23 is shorter than the update cycle of a satellite signal,and is set to, for example, one half, one fifth, and one tenth.

When the selection result (Select_SW) output from the correctionselector 26 is 0 and it is selected at Step S202 that the position ofthe own vehicle is not corrected, the correction setting unit 23 setsthe counted time value to the duration of detection of the position jump(T_Count), and outputs it to the position jump determining unit 25 (StepS206). Then, the correction setting unit 23 outputs to the autonomousnavigation processor 24 the autonomous maintaining signal (At_M)instructing that the autonomous navigation position (At_Pos) and theown-vehicle direction (Direction) should be maintained (Step S207), andends a series of the operations.

When the selection result (Select_SW) is 1 and it is selected at StepS202 that the position of the own vehicle is to be corrected, thecorrection setting unit 23 sets the satellite positioning position(GNSS_Pos) to the corrected position (C_GNSS_Pos) (Step S203), and setsthe satellite positioning direction (GNSS_Direction) to the correcteddirection (C_Direction) (Step S204). Then, the collection setting unit23 resets to 0 the duration of detection of the position jump (T_Count)(Step S205), and ends a series of the operations. In other words, thecollection setting unit 23 ends the operations by determining that theposition jump has been overcome using the satellite positioning positionand the satellite positioning direction that have been corrected,instead of the autonomous navigation position (At_Pos) and theown-vehicle direction (Direction), respectively.

FIG. 5 is a functional block diagram illustrating the configuration ofthe position jump determining unit 25. As illustrated in FIG. 5, theposition jump determining unit 25 includes a positional differenceprocessor 51, a threshold determining unit 52 that determines athreshold for determining occurrence of the position jump using athreshold map, and a comparator 53.

The positional difference processor 51 receives the satellitepositioning position (GNSS_Pos) and the autonomous navigation position(At_Pos). Each of the positions indicates a position on atwo-dimensional plane. The positional difference processor 51 computes adistance between the two positions, and outputs it as a positionaldifference (Dif_Cal). The satellite positioning position and theautonomous navigation position may be provided as positions not on thetwo-dimensional plane but on a three-dimensional plane.

The threshold determining unit 52 receives the duration of detection ofthe position jump (T_Count) set by the correction setting unit 23, anddetermines the threshold for determining occurrence of the position jumpusing the threshold map stored in a memory such as a non-volatilememory. In other words, the duration of detection of the position jump(T_Count) is defined by the time counted by the correction setting unit23, and the number of pulses is counted until the counter is reset. Thismeans that the counting continues while an unacceptable level of aposition jump continues, that is, a large position jump in anunacceptable level continues over a long time and the satellitepositioning position (GNSS_Pos) and the satellite positioning direction(GNSS_Direction) cannot be used. If this continues, the vehicle isautomatically driven only depending on the autonomous navigationposition (At_Pos) and the own-vehicle direction (Direction), and thusthe target driving route may deviate from its original. Here, when theduration of detection of the position jump becomes prolonged, conditionsfor determining the position jump are relaxed to forcibly correct theposition of the own vehicle. Specifically, as the duration of detectionof the position jump is longer, the threshold for determining occurrenceof the position jump (Dif_Thresh) is set larger.

The comparator 53 compares the positional difference (Dif_Cal) computedby the positional difference processor 51 with the threshold fordetermining occurrence of the position jump (Dif_Thresh) determined bythe threshold determining unit 52. When the threshold for determiningoccurrence of the position jump is larger than the positionaldifference, that is, when the positional difference falls within thethreshold for determining occurrence of the position jump, thecomparator 53 outputs 0 as the result of the determination on positionjump (PosJump_Judge) indicating that the satellite positioning positionis represented by an acceptable value (no occurrence of the positionjump or occurrence of an allowable position jump). When the thresholdfor determining occurrence of the position jump is smaller than thepositional difference, that is, when the positional difference does notfall within the threshold for determining occurrence of the positionjump, the comparator 53 outputs 1 as the result of the determination onposition jump (PosJump_Judge) indicating that the satellite positioningposition is represented by an unacceptable value (occurrence of anunacceptable position jump).

The threshold map to be used by the threshold determining unit 52 may bea map in which a threshold for determining occurrence of a position jumplinearly increases with respect to increase in duration of detection ofthe position jump, a stepped map in which the threshold is maintainedconstant during a relatively shorter duration and a relatively longerduration of detection of the position jump and the threshold linearlyincreases only between the end of the relatively shorter duration andthe start of the relatively longer duration, or a map in which thethreshold non-linearly increases. In consideration of sensing propertiesof the various sensors used in autonomous navigation, a map is createdaccording to the precision of the autonomous navigation.

FIG. 6 is a flowchart for describing an operation of the correctionselector 26. The correction selector 26 selects whether the position isto be corrected on the basis of the result of the determination onposition jump (PosJump_Judge) output from the position jump determiningunit 25 and the precision indicator (GNSS_Quality) output from thesatellite positioning receiver 21, and outputs the selection result(Select_SW) (Step S301).

FIG. 7 is a diagram indicating with a matrix the selection conditionsfor selecting whether to correct the position. FIG. 7 indicates fourpossible combinations of (i) two values representing results of thedetermination on position jump, that is, 0 (no occurrence of a positionjump or occurrence of an allowable position jump) and 1 (occurrence ofan unacceptable position jump), and (ii) two values of the precisionindicators, that is, 0 (lower precision) and 1 (higher precision).

The correction selector 26 selects to correct a position when the resultof the determination on position jump is 0 and the precision indicatoris 0, and outputs 1 as the selection result. Furthermore, the correctionselector 26 selects to correct a position when the result of thedetermination on position jump is 0 and the precision indicator is 1,and outputs 1 as the selection result. Furthermore, the correctionselector 26 selects not to correct a position when the result of thedetermination on position jump is 1 and the precision indicator is 0,and outputs 0 as the selection result. Furthermore, the correctionselector 26 selects to correct a position when the result of thedetermination on position jump is 1 and the precision indicator is 1,and outputs 1 as the selection result. The selection by the correctionselector 26 is summarized as follows:

(1) when the satellite positioning precision indicator indicates “higherprecision”, the current position of the own vehicle obtained byautonomous navigation is corrected to a position of the own vehicleobtained by the satellite positioning irrespective of the result of thedetermination on position jump output from the position jump determiningunit 25;

(2) when the satellite positioning precision indicator indicates “lowerprecision” and the position jump determining unit 25 determines nooccurrence of the position jump or occurrence of an allowable positionjump as the result of the determination on position jump, the currentposition of the own vehicle obtained by autonomous navigation iscorrected to a position of the own vehicle obtained by the satellitepositioning; and

(3) when the satellite positioning precision indicator indicates “lowerprecision” and the position jump determining unit 25 determinesoccurrence of an unacceptable position jump as the result of thedetermination on position jump, the current position of the own vehicleobtained by autonomous navigation is maintained.

Since computation of the moving direction of the own vehicle by thedirection processor 22 and computation of the autonomous navigationposition and the own-vehicle direction by the autonomous navigationprocessor 24 can be performed by a conventional computation method, thedescription thereof will be omitted.

Furthermore, the direction processor 22, the correction setting unit 23,the autonomous navigation processor 24, the position jump detecting unit25, and the correction selector 26 in the own-vehicle position detector9 may be implemented by hardware or by executing predetermined softwarein an arithmetic processing unit such as a central processing unit(CPU).

(Automatic Steering Control Based on Own-Vehicle Position Information)

As described with reference to FIG. 1, since the highly preciseown-vehicle position information detected by the own-vehicle positiondetector 9 is provided to the automatic steering controller 11, theautomatic steering controller 11 provides automatic steering andcontrols the velocity and the brake for the steering wheel 3 so that theself-driving vehicle 1 is capable of automatic driving.

Although imprecise own-vehicle position information destabilizes thebehavior of the self-driving vehicle 1, the own-vehicle positiondetector 9 according to the present invention compares a positionaldifference between a satellite positioning position and an autonomousnavigation position with a threshold for determining occurrence of theposition jump, and corrects the autonomous navigation position to thesatellite positioning position when the threshold is larger than thepositional difference, that is, when the positional difference fallswithin the threshold. Accordingly, the behavior of the self-drivingvehicle 1 will be stabilized without any sudden steering operation.

This advantage will be described with reference to FIGS. 8 to 11. FIG. 8schematically illustrates a relationship between a threshold fordetermining occurrence of the position jump (Dif_Thresh) and apositional difference (Dif_Cal) by plotting satellite positioningpositions (GNSS_Pos) using rhombuses and autonomous navigation positions(At_Pos) using black circles. In FIG. 8, the satellite positioningpositions almost match the autonomous navigation positions in a normalstate. However, when the position jump occurs and the positionaldifference (Dif_Cal) between the satellite positioning position and theautonomous navigation position (indicated by a black triangle) is largerthan the threshold for determining occurrence of the position jump(Dif_Thresh), the position jump determining unit 25 determinesoccurrence of the position jump. FIG. 8 illustrates a position jumpdetermining area indicated by a dashed line that is an area with aradius of the threshold for determining occurrence of the position jump.When a satellite positioning position is within this area, the positionjump determining unit 25 determines no occurrence of the position jump.

FIG. 9 illustrates the subsequent operations after determining that theposition jump occurs in FIG. 8. When the satellite positioning precisionindicator indicates “lower precision”, the correction selector 26maintains the current position of the own vehicle obtained by autonomousnavigation. Thus, the satellite positioning position is rejected. Here,the own vehicle is driven along the target driving route, and theposition jump is not detected with the next updating timing of thesatellite signal. Then, the own vehicle proceeds further, and theoccurrence of a position jump is determined with the updating timingafter the next.

FIG. 10 is a diagram indicating a conventional steering wheel angleusing automatic steering when a position jump occurs, and a steeringwheel angle to which the present invention has been applied,specifically, a diagram indicating temporal change characteristics AT10(dashed line) of the conventional steering wheel angle, and temporalchange characteristics AT1 (solid line) of the steering wheel angle towhich the present invention has been applied. As illustrated in FIG. 10,conventionally, a sudden steering operation occurs when a position jumpis detected and suddenly the steering wheel returns to its originalposition after sudden change in the steering wheel angle, thusdestabilizing the vehicle behavior. In contrast, in the case where thepresent invention has been applied, even when a position jump occurs, asudden steering operation does not occur because the current position ofthe own vehicle obtained by autonomous navigation is maintained, and thevehicle behavior is stable.

FIG. 11 is a diagram indicating lateral accelerations when a positionjump occurs and to which the present invention has been applied,specifically, a diagram indicating temporal change characteristics G10(dashed line) of the conventional lateral acceleration, and temporalchange characteristics GT1 (solid line) of the lateral acceleration towhich the present invention has been applied. As illustrated in FIG. 11,detection of a position jump conventionally causes a lateralacceleration subject to a sudden steering operation to occur, whereas inthe case where the present invention has been applied, even when aposition jump occurs, neither a sudden steering operation nor lateralacceleration occurs.

(Countermeasures when Position Jump Continues)

Next, the countermeasures when a position jump continues will bedescribed with reference to FIGS. 12 and 13. FIG. 12 schematicallyillustrates a misalignment in detecting a position jump by aconventional method when the position jump occurs.

In FIG. 12, the satellite positioning positions are plotted usingrhombuses and the autonomous navigation positions are plotted usingblack circles, in the same manner as FIG. 8. Furthermore, the positionjump determining areas are indicated by respective dashed lines. Whenthe position jump continues and the satellite positioning positionscannot be used, the autonomous navigation positions are misaligned fromthe actual own-vehicle positions depending on the precision ofautonomous navigation in the driving based on the autonomous navigationpositions. In other words, a track D2 of the positions of the ownvehicle obtained by autonomous navigation is misaligned from an actualtrack D1 of the own vehicle as illustrated in FIG. 12. Since theposition jump determining areas are not dynamically changed in theconventional detection of a position jump, even when the own vehiclepasses through an area ER where the position jump occurs and thesatellite positioning positions approximate to an area closer to theactual own-vehicle positions, in the case where the position jumpdetermining areas are narrow, the satellite positioning position isrejected and the misalignment in the positions of the own vehicleobtained by autonomous navigation will not be persistently corrected.

FIG. 13 schematically illustrates a misalignment in detecting a positionjump according to the present invention when the position jump occurs.As illustrated in FIG. 13, the position jump determining areas aredynamically changed by increasing a threshold for determining occurrenceof a position jump as a duration of detection of the position jump islonger in detecting the position jump according to the presentinvention. Thus, when the own vehicle passes through the area ER wherethe position jump occurs and the satellite positioning positionsapproximate to the area closer to the actual own-vehicle positions,since the position jump determining areas are wider, the autonomousnavigation positions can be corrected to the satellite positioningpositions, and the track D2 of the positions of the own vehicle obtainedby autonomous navigation can be corrected to a track D3 closer to theactual own-vehicle positions.

(Examples of Other Precision Indicators)

Although “Fix” and “Float” in the RTK measurement are used as theprecision indicators output by the satellite positioning receiver 21according to the embodiment of the present invention, the precisionindicators in the satellite positioning are not limited to these.

In other words, since the positioning precision varies according to ageometric positional relationship between an object to be measured (ownvehicle) and a satellite and it also varies from moment to momentaccording to a position of the object and the time, dilution ofprecision (DOP) values have been proposed as indicators forunderstanding the positioning precision.

Examples of the DOP values include horizontal dilution of precision(HDOP) numerically representing the positional precision in a horizontaldirection, and vertical dilution of precision (VDOP) numericallyrepresenting the positional precision in a vertical direction. Forexample, the favorable HDOP is 2.0 or lower. When the satellitepositioning receiver 21 determines the HDOP to be 2.0 or lower, it mayoutput 1 indicating higher precision as a precision indicator. When theHDOP exceeds 2.0, the satellite positioning receiver 21 may output 0indicating lower precision as a precision indicator.

When the DOP is used as an precision indicator, the satellitepositioning receiver 21 is not limited to a receiver for RTKmeasurement.

(Variations)

Although the structure according to the embodiment of the presentinvention adopts the own-vehicle position detector 9 and the automaticsteering controller 11 as different devices as illustrated in FIG. 1,the own-vehicle position detector 9 and the automatic steeringcontroller 11 may be incorporated into one device.

Furthermore, not all the constituent elements of the own-vehicleposition detector 9 but at least the position jump determining unit 25and the correction selector 26 may be incorporated into the automaticsteering controller 11.

The embodiment according to the present invention can be appropriatelymodified and omitted within the scope of the invention.

The invention claimed is:
 1. A vehicle position detector comprising: asatellite positioning receiver; an autonomous navigation processor thatoutputs an own-vehicle position detected by said autonomous navigationas an autonomous navigation position; a processor that determinesoccurrence of a position jump on the basis of a positional differencebetween said autonomous navigation position and a satellite positioningposition detected by said satellite positioning receiver using saidsatellite positioning; and a selector that selects one of saidautonomous navigation position and said satellite positioning positionon the basis of positioning precision of said satellite positioning thatis output by said satellite positioning receiver, and a result of saiddetermination on position jump by said processor, wherein said vehicleposition detector outputs one of said autonomous navigation position andsaid satellite positioning position as said own-vehicle position on thebasis of a result of said selection by said selector.
 2. The vehicleposition detector according to claim 1, wherein said processor compares,with a threshold, said positional difference between said satellitepositioning position and said autonomous navigation position, anddetermines when said positional difference falls within said thresholdthat said satellite positioning position is represented by an acceptablevalue and determines when said positional difference does not fallwithin said threshold that said satellite positioning position isrepresented by an unacceptable value.
 3. The vehicle position detectoraccording to claim 2, wherein said selector selects said satellitepositioning position as said own-vehicle position when said satellitepositioning position is represented by said acceptable value.
 4. Thevehicle position detector according to claim 2, wherein said positioningprecision of said satellite positioning is defined by a first precisionand a second precision lower than said first precision, and saidselector selects said satellite positioning position as said own-vehicleposition irrespective of said result of said determination on positionjump by said processor, when said positioning precision is defined bysaid first precision.
 5. The vehicle position detector according toclaim 2, wherein said positioning precision of said satellitepositioning is defined by a first precision and a second precision lowerthan said first precision, and said selector selects said satellitepositioning position as said own-vehicle position, when said positioningprecision is defined by said second precision and said satellitepositioning position is represented by said acceptable value.
 6. Thevehicle position detector according to claim 2, wherein said positioningprecision of said satellite positioning is defined by a first precisionand a second precision lower than said first precision, and saidselector selects said autonomous navigation position as said own-vehicleposition, when said positioning precision is defined by said secondprecision and said satellite positioning position is represented by saidunacceptable value.
 7. The vehicle position detector according to claim2, wherein when continuing to determine that said satellite positioningposition is represented by said unacceptable value, said processorchanges said threshold into a larger value on the basis of a durationduring which said processor continues to determine that said satellitepositioning position is represented by said unacceptable value.
 8. Thevehicle position detector according to claim 1, wherein said vehicleposition detector outputs: together with said satellite positioningposition, a satellite positioning direction obtained on the basis ofsaid satellite positioning position, and together with said autonomousnavigation position, an own-vehicle direction obtained by saidautonomous navigation.
 9. A vehicle position detecting method,comprising: (a) detecting an own-vehicle position by satellitepositioning as a satellite positioning position; (b) detecting saidown-vehicle position by autonomous navigation as an autonomousnavigation position; (c) determining occurrence of a position jump onthe basis of a positional difference between said satellite positioningposition and said autonomous navigation position; and (d) selecting oneof said autonomous navigation position and said satellite positioningposition on the basis of positioning precision of said satellitepositioning and a result of said determining in (c), wherein one of saidautonomous navigation position and said satellite positioning positionis output as said own-vehicle position on the basis of a result of saidselecting in (d).